Alloy



Patented May 10, 1938 ALLOY Marvin J. Udy, Niagara Falls, N. Y.,assignor, by mesne assignments, to Monsanto Chemical Company, a.corporation of Delaware NoDrawing. Application October 31, 1934, SerialNo. 750,821

lClaim.

This invention relates to alloys of iron, chromium and phosphorus and toa process of producing the same.

One object of my invention is the provision of an alloy containing theelements iron, chromium and phosphorus in major proportion. It relatesto an alloy or a series of alloys useful for introducing these elementsinto molten iron or steel as in the production of alloy steels. A stillfurther object is the production of chrome-iron alloys low in carbon.

I am aware that it has been proposed to produce alloy steels containing,in addition to chromium, a relatively small proportion of phosphorus,the proportion recommended being from 0.15% to 0.5% phosphorus togetherwith from 3% to 30% chromium. Such materials are special purpose steelsrecommended for certain uses and are not intended to serve for thesubsequent production of alloy steels. 1

In the production of rustless or stainless iron or steel it isparticularly necessary to obtain a low carbon content in the finishedproduct in order that a workable material be had. This is accomplishedin various ways, the most usual being the use of low-carbonferro-chromium as the alloying constituent which supplies the chromiumin the alloy.

Low-carbon ferrochromium is, however, difiicult to make and isexpensive, hence a cheap method of producing the same was very muchdesired.

I have now found that if a chrome-iron alloy containing appreciableproportions of phosphorus is produced in the electric furnace, the alloywill contain much less carbon than in the absence of phosphorus. Inother words, the phosphorus in my alloy effectively minimizes theabsorption of carbon.

I have also found that the carbon absorbed by the alloy duringmanufacture depends upon the amount of phosphorus present. In otherwords, by increasing the phosphorus, I decrease the carbon content ofthe alloy. This discovery constitutes an eifective control over thecarbon content, which discovery may be utilized in various ways.

Several examples will illustrate my process and the product obtainedthereby.

Example I Mix together a furnace burden consisting of phosphate rock,silica, chrome ore and coke in the proportions of 53 pounds of phosphaterock, 47 pounds of chrome ore, 12 pounds of S102 pebble, and 21 poundsof coke. Charge to an electric arc furnace and melt down, usingapproximately 100 volts. After the ore has been completely fused, thefurnace is tapped and slag and metal are withdrawn. The amount 01 metalobtained weighed 15.8 pounds, indicating a recovery of 82% of thetheory. The metal analyzed as follows:

From the weights of materials charged to the furnace, I obtained arecovery in the alloy of 46.5% of phosphorus and 85.5% of chromium inthe burden. The remainder of the phosphorus, except that entering theslag, was volatilized. The chromium not recovered in the alloy wasvolatilized.

Example II To a furnace burden such as was used in Example I above, Iadded 3.3 pounds of scrap iron.

This burden was then melted in the same manner, the furnace tapped, andthe metal and slag separated.

The metal recovered amounted to 89% of the theory and analyzed asfollows:

Percent Phosphorus i 18.4 Chromium 46.9 Iron 32.35

Carbon 2.19

Silicon 0.44

From the weights of material charged to the furnace, I obtained arecovery of 64.5% of phosphorus and 91.5% of chromium.

Example III From a burden consisting of. 60 pounds of chrome orecontaining 31% of chromium and 11.26% iron, 60 pounds of Florida pebblephosphate rock, and 36 pounds of coke, I obtained,

upon smelting, 16 pounds of an alloy analyzing as follows:

Percent Phosphorus 15.05 Chromium 48.82 Silicon 4.24 Carb n a 1.41

The smelting operation was carried out in a furnace supplied with 100volt alternating current. To aid in maintaining a fusible slag, I addeda lime silicate slag to the furnace both at the/beginning and at the endof the run. A slag suitable for this purpose may be blast or electricfurnace slag in which the SiO2CaO ratio is in the neighborhood of 0.7.If no such slag is available, I may add the constituents thereof, thatis, lime and silica, directly to the burden in the required proportions.

From my observations on this operation it appears as if a refining ofthe metal with elimination of carbon takes place. This is believed to bedue to the character of the slag employed. Additional refining may becarried out by exposing the molten metal in the furnace to the action ofthe lime-silica slag for a longer period of time. This refiningoperation serves to decrease the carbon content of the alloy, andapparently increases the silicon content at the same time.

The present alloy is particularly valuable from the standpoint of theproduction of low-carbon ferro-chrome. This material may be produced byrefining the alloys described in the examples mentioned above, under a.basic oxidizing slag. By this means the phosphorus and carbon contentsof the alloy are reduced. Such a slag is.

made up by using the ordinary lime-silica slag and adding iron ore ormill scale to the slag during the refining operation. In some cases theaddition of chrome ore to the slag may be found desirable.

By suitably proportioning the constituents of the burden, I am able toproduce alloys varying in composition. Alloys which Ihave produced in myprocess vary in phosphorus content between 3% and 20%; in chrome contentbetween 15% v and and in iron content between 25% and These threeconstituents comprise the major ingredients in my alloy. The minorconstituents will consist principally of carbon and silicon, the formervarying from 0.5% to 5.0% and the latter varying between 0.05% and 6.5%,depending upon the character of the operation and the proportions of themajor constituents present in the alloy.

My observations have led me to believe that the proportion of phosphoruspresent is of 0011- trolling significance with regard to the amount ofcarbon present in the alloy. I have found that the increasing amounts ofphosphorus in my alloy makes for. a lower carbon content of the same. Inthis regard, silicon, although a minor constituent, is also ofimportance. The content of silicon is usually less than 6.5%, althoughit may be varied somewhat. Increasing the silica content of the burdenand prolonging the smelting time increases the silicon content of thealloy. In a preferred form of my alloy the ratio of chromium tophosphorus will be greater than one and less than four, and the carboncontent will'be between 1% and. 3.5%.' If a small proportion of silicon,say 4% to 6%, be present in this alloy, the carbon content willgenerally be If the chromium to phosphorus ratio be greater than fourand less than, say, seven, the carbon content will be higher, that is,between 3.5% and 4.5%. As above stated, the carbon content in this caseis also influenced by the silicon present, larger amounts of silicondecreasing the carbon to the lower values of this range.

Having nowdescribed my invention and the manner in which it may be used,it will be apparent that it is susceptible to various changes andmodifications without departingfrom the spirit thereof, and I desire,therefore, that it be not limited except as necessitated by the priorart or as specifically set out in the appended claim.

What I claim is:

An alloy comprising chromium 15% to 60%; phosphorus 3% to 20%; silicon4% to 6%; the balance being iron.

. MARVIN J. UDY.

